Starter jaw release



United States Patent 2,913,908 STARTER JAW RELEASE Abe J. Perle, Verona,N.J., assignor to Bendix Aviation Corporation, Utica, N .Y., acorporation of Delaware Application July 1, 1957, Serial No. 669,171 j 7Claims. (Cl. 74-7) The present invention relates to engine starters andmore particularly concerns a starter having an overrunning clutch.

Turbine engines must be operated at high speeds in order to start.Turbine type starters have proved satisfactory since capable of rapidlyrotating the turbine engines to high speeds. In order to avoid meshingproblems between the starter jaw and the engine jaw such starters areconnected to the engine and have an overrunning or one-way clutch sothat starter torque is transmitted to the engine but engine torque isnot transmitted to the starter gear train and turbine. Thus, upon theengine speed exceeding the starter speed, the clutch permits the engineto overrun the starter. In some instances, however, the overrunningclutch has been known to se.ze and not to permit the engine to overrunthe starter. Such a malfunction can put a drag on the engine or cancause the engine to drive the starter. In either event, serious damageto either the engine or starter can result.

The primary object of the present invention is to prevent the aforenotedpossibility of damage by providing improved automatic disconnect meansbetween an engine and its starting means whereby, upon malfunctioning ofthe starter, a break in the drive train will result.

A further object is the provision of improved means to retract orunlatch the starter jaw when the engine torque, attempting to drive aninoperative starter, exceeds a safe value.

An additional object is to provide an improved reverse-overload releasemechanism including a Belleville spring whereby a splined-mountedstarter jaw is permanently moved out of engagement with an engine jawwhen the engine jaw tends to urge the starter jaw out of engagement.

The accomplishment of the above objects, along with the features andadvantages of the present invention, will be apparent from the followingdescription and the accompanying drawing wherein an embodiment of theinvention is illustrated by way of example.

The accompanying drawing is a side elevation in cross section of astarter embodying the invention and shows a starter jaw normally engagedwith an engine jaw and re verse torque disengaging means which operatesif the overrunning clutch fails.

The present invention provides improved means whereby the high speedtorque output of the starter is sat isfactorily transmitted in onedirection to the engine and whereby the starter will be disconnectedfrom the engine when a small predetermined torque is applied in thereverse direction. In the disclosed embodiment, the starter jaw is heldin driving connection with an engine jaw by a positioning mechanismhaving a Belleville spring. The starter jaw is mounted by a splineconnection on a gear drive member which is coupled to starter gearing byan overrunning clutch. Upon reverse torque, the starter jaw is urgedaxially away from the engine jaw by the jaw teeth separating action tocause the positioning mechanism to unlatch and to permit spring means toaxially Patented Nov. 24, 1959 slide the starter jaw permanently out ofcontact with the engine jaw.

Referring to the drawing, it is apparent that torque is transmitted fromthe annular gearing member 11 outwardly through the well-known one-waysprag-type clutch 13 to the clutch cover or drive plate 15 which carriesthe splined annular starter jaw 17. Member 11 is connected throughsuitable reduction gearing (not shown) to a high speed turbine (notshown). Other conventional and wellknown means having a one-way oroverrunning clutch can be used to rotate'the annular portion of clutchcover 15 or a similar drive member. The cover 15 having outer and innerannular sections connected by a transverse wall is rotatably mounted bybearings 21 carried by an axial extension 23 of gear member 11. Thestarter jaw 17 has teeth which mesh with the teeth of engine jaw 25which is connected by splines 27 in its axial tubular part to engineshaft 29. These mating jaws 17 and 25 are saw-toothed in circumferentialprofile and have the conventional axialextending and inclined faces.Mounting flange or head 31 is attached by a suitable coupling (notshown) to starter housing 33 so that the starter can be mounted on theaircraft engine. A stationary starter shaft 34 has the gear member 11rotatably mounted thereon.

The starter jaw positioning and retracting arrangement includes anannular adjusting ring 35 threaded and locked on the splined-mountedstarter jaw 17 and an annular Belleville spring retainer cuff 37 whichis axially slidable on ring 35. The pair of Belleville springs 39 aremounted between an inwardly-extending lip 40 of the cufi 37 and anannular inner edge 41 of adjusting ring 35. The Belleville springs thusare inclined axially toward the starter jaw. Ring 35 also has aninwardly-extending transverse collar or lip 43 which retains anaxially-extending coil spring 44 against the transverse splined part 45of plate 15. Collar 43 is so positioned by lock ring 46. Thisarrangement is such that the spring 44 does not snap the Bellevillesprings 39 through center. Although coil spring 44 bearing againstcollar 43 tends to urge the splined-mounted annular jaw structureincluding starter jaw ring 17 and adjusting rings 35 rearwardly over thespline connection, the annular cuff 37 and Belleville springs 39 ineffect constitute an opposing rigid structure, bearing against thetransverse face of the plate 15, and hence prevent any axial inwardmovement'because the force of coil spring 44 is not suflicient toovercome the Belleville springs 39.

A heavy coil spring 51 is retained by cup 52 within starter jaw member25 which is splined-mounted in the bore of engine shaft 29. Spring 51 ismuch stifier than the Belleville springs 39 and restrains the starterjaw from axial movement to the right when there are axial separat ingforces between the two slidable starter and engine jaws 17 and 25. Suchaxial separating forces occur when the engine attempts to drive thestarter through the inclined surfaces of the mating saw-tooth jaws. Itis to be noted that engine jaw arrangement is such that the engine jaw25 cannot move to the left when the starter jaw 17 is stretched becauseof the rigid structure provided by bolt 55 and cup 57. Bolt 55 isaxially threaded into the engine shaft 29 and cup 57 is positioned inthe recess 58 in the axial tubular part of starter jaw 25.

Under conditions of normal operation, the starter cranks the engine to aspecific starter cut-ofi speed. The engine then continues to accelerateto a higher normal operating speed level. clutch 13 disengages at apredetermined speed after the engine is started, the starter power trainincluding .driving member 11 normally coasts .to rest. However, if theone-way sprag clutch 13 does not disengage orotherwise malfunctions, theengine jaw 25 drives the starter jaw 17 with the driving torque beingtransmitted be- Because the one-way sprag tween the angular faces of thejaw teeth rather than through the axial faces of the teeth. This sets upaxial separating forces between the two slidable jaws. Engine jaw 25 isbacked up by spring 51 which is a much stiffer spring than theBelleville type springs 39. Thus, the separating forces between jaws 17,25 will result in proportionally small axial motion of the engine jaw 25to the right and large axial motion of the starter jaw 17 to the left.Belleville springs 39 are so designed as to snap through center when theaxial load caused by excessive starter drag torque reaches a dangerouslevel. When the Belleville type springs are snapped through center andcuff 37 slides to the right, the starter jaw 25 is rapidly retracted inan axial direction by jaw disengagement spring 44 which bears againstthe collar 43 and slides the starter jaw to the left over its splines.Starter jaw 17 is thus held in a position sufiiciently removed fromengine jaw 25 so that re-engagement of the jaws is impossible and theengine operation can continue without transmission of any torque bacltthrough the malfunctioned starter.

Since the starter is unlatched or retracted sufficiently so that thestarter jaw cannot engage the engine jaw, the starter cannot crank theengine when it is next desired to start up, thus signalling the fact ofa starter malfunction. The starter is then removed and the source ofmalfunction is corrected. Finally, the starter jaw mechanism is recockedand the starter is again mounted so that the jaws are engaged forstarting.

From the foregoing, it is apparent that reverse torque actuates theunlatching or retraction arrangement and permanently retracts thestarter jaw so that it cannot contact the engine jaw or be driventhereby. It is to be noted that the snap action of the Bellevillesprings permits rapid retraction of the starter jaw so that racheting oftip part of the saw teeth of the jaws is minimized. Thus, in the eventof some type of starter malfunction, after the engine has been started,means have been provided to assure continuation of engine operationwithout damage to the engine or additional damage to the starter andfurther to signal the existence of trouble to the pilot at the time heattempts operation of the starter at a later date, without effectingfurther damage. It is to be appreciated that transmission of torque backthrough the malfunctioned starter and drag on the engine is prevented bythe present invention when the engine torque attempting to drive theinoperative starter exceeds a predetermined safe value.

It is to be understood that changes can be made in the disclosedembodiment of the invention by persons skilled in the art withoutdeparting from the invention as defined by the appended claims.

What is claimed is:

1. An engine starting system comprised of an engine starter having anoverrunning clutch and a driving member connected to be rotated in apredetermined direction through said overrunning clutch, a driven memberadapted for connection to an engine shaft and having engine jaw teeththereon, a starter jaw member carried by said driving member and movableaxially relative thereto without rotation, said starter jaw memberhaving starter jaw teeth thereon, said teeth being so constructed as toseparate when rotation is opposite to said predetermined direction,positioning means including snap action device cooperating with saiddriving member to position said starter teeth in engagement with saidengine jaw teeth so that said teeth are normally engaged and said drivenmember can normally drive said driving member which is connected to saidoverrunning clutch, said positioning means being responsive to apredetermined reverse torque and, when so actuated, permitting saidstarter jaw member to be movable axially, and spring means forretracting said starter jaw teeth out of contact with said engine jawteeth when said positioning means is actuated by said reversetor'que.

2. A reverse torque disconnect mechanism for use with an engine startercomprising a driving member, a driven member, a starter jaw membersplined-connected to said driving member and movable axially relativethereto without rotation, said driven member having an engine jawportion mating with said starter jaw member, spring means for urgingsaid starter jaw member out of engagement, restraining means including aBelleville spring for normally positioning said starter jaw member intoengagement and for normally preventing said spring means from urgingsaid starter jaw member out of engagement, said restraining means beingresponsive to torque in a reverse direction exceeding a predeterminedvalue and operative to permit said spring means to retract said starterjaw member from contact with said engine jaw portion, and said drivenmember having a spring arranged to oppose axial movement of said drivenmember away from said driving member so that the jaw member actuatessaid Belleville spring.

3. For use in an engine starter, the combination com prising outputgearing, a drive plate, an overrunning clutch connecting said driveplate with said output gearing for transmitting torque in one direction,a starter jaw element splined-mounted to said drive plate and movableaxially relative thereto without rotation, an engine jaw member adaptedto mate with said starter jaw element, reverse torque means normallypositioning said starter jaw element into engagement with said enginejaw member, spring means for axially biasing said starter jaw elementout of engagement with said engine jaw member, and said reverse torquemeans axially opposing and normally preventing said spring means fromdisen.

gaging said starter jaw element and said engine jaw member, said reversetorque means being responsive to a predetermined reverse torque andaxially operated by said starter jaw element to permit said spring meansto disengage said starter jaw element from said engine jaw member.

4. An engine starter comprised of a gear train and an overrunningclutch, a starter jaw plate having an axial tubular extension and beingoperatively arranged to be rotated through said clutch, an annularstarter jaw member splined-mounted on said extension, a sleeve slidablymounted on said starter jaw member, a Belleville spring extendingbetween said sleeve and said starter jaw member, said sleeve andBelleville spring being arranged to oppose inward movement of saidstarter jaw member until a predetermined axial force is exerted on saidstarter jaw member when said Belleville spring snaps through center,spring means extending between said tubular extension and said starterjaw member and arranged to axially retract said starter jaw member whensaid Belleville spring. is snapped through center by said predeterminedforce.

5. In an engine starting system having an overrunning clutch drivinglyconnected to a transverse drive plate which has an axial extension, theimprovement comprising an annular starter jaw member spline-mountedaxially on said axial extension, positioning means positioning normallysaid starter jaw member into engagement with a mating engine jaw, springmeans urging said starter jaw member inwardly, said positioning meansincluding a snap action device which is operable by a predeterminedreverse axial force, said positioning means being so constructed andarranged that said spring means can position said starter jaw member outof engagement with a mating engine jaw when said snap action device isoperated whereby, when said starter jaw member is being driven, theaxial force generated will operate said snap-action device and saidstarter jaw member will be retracted.

6. In an engine starting system having an overrunning clutch drivinglyconnected to a transverse drive plate which has an axial extension, theimprovement comprising an annular starter jaw member spline-mountedaxially on said axial extension, positioning means cooperating with theouter transverse face of said drive plate and connected to theaxially-inner edge of said annular starter jaw member for normallypositioning said starter jaw member into engagement with a mating enginejaw adjacent the outer edge of said axial extension, spring means urgingsaid starter jaw member inwardly, said positioning means including asnap action device which is operable by a predetermined axially-inwardforce, said positioning means being so constructed and arranged thatsaid spring means can position said starter jaw member out of engagementwith a mating engine jaw adjacent the outer edge of said axial extensionwhen said snap action device is operated whereby, when said starter jawmember is being driven, the axial force generated will operate saidsnap-action device and said starter jaw member will be retracted.

7. The engine starter comprised of a gear driving member connectedthrough an overrunning clutch to a jaw plate, said jaw plate having atransverse face and an axial extension, an annular starter jaw structuremounted on said extension by means of an axial spline connection, saidstarter jaw structure having a starter jaw extending axially from theouter edge thereof, an engine jaw engaging said starter jaw normally, acoil spring extending axially between said starter jaw structure andsaid extension and urging said starter jaw structure inwardly towardsaid transverse face of said jaw plate, a sleeve slidably mounted onsaid starter jaw structure, a Belleville spring extending between saidsleeve and said starter jaw structure and positioning the inner end ofsaid sleeve in contact with said transverse face of said jaw plate, saidBelleville spring being such as to prevent said coil spring fromsnapping said Belleville spring through center, spring means back ofsaid engine jaw, said spring means being constructed and arranged so asto exert a greater axial resistance than said Belleville spring whereby,when an engine attempts to drive the starter, the axial force at saidjaws will axially move said starter jaw and cause said Belleville springto snap through center and said coil spring will move said starter jawstructure away from said engine jaw, said sleeve and Belleville springbeing constructed so as to permit said starter jaw structure to be moveda distance such that said starter jaw and said engine jaw cannot contacteach other.

References Cited in the file of this patent UNITED STATES PATENTS2,665,674 Metsger et a1. Jan. 12, 1954 2,721,482 Shank et a1 Oct. 25,1955 2,728,252 Connell Dec. 27, 1955 2,752,023 Cain et a1. June 26, 1956

